package Year22_Month03.day30;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()){
            int n = sc.nextInt();//用来保存初始天数
            int m = sc.nextInt();//用来保存结束天数
            long[] arr = new long[m+1];
            int index = 1;
            while(index <= m){
                if(index == 1 || index == 2){
                    arr[index] = 1;
                }else{
                    arr[index] = arr[index - 1] + arr[index - 2];
                }
                index++;
            }
            int res = 0;
            for (int i = n; i <= m; i++) {
                res += arr[i];
            }
            System.out.print(res + " ");
        }
    }
}
